Btrfs: leave btree locks spinning more often

btrfs_mark_buffer dirty would set dirty bits in the extent_io tree
for the buffers it was dirtying.  This may require a kmalloc and it
was not atomic.  So, anyone who called btrfs_mark_buffer_dirty had to
set any btree locks they were holding to blocking first.

This commit changes dirty tracking for extent buffers to just use a flag
in the extent buffer.  Now that we have one and only one extent buffer
per page, this can be safely done without losing dirty bits along the way.

This also introduces a path->leave_spinning flag that callers of
btrfs_search_slot can use to indicate they will properly deal with a
path returned where all the locks are spinning instead of blocking.

Many of the btree search callers now expect spinning paths,
resulting in better btree concurrency overall.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 14 insertions, 3 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index c427011..b83a45d 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -134,6 +134,7 @@ static noinline int insert_inline_extent(struct btrfs_trans_handle *trans,
 	if (!path)
 		return -ENOMEM;
 
+	path->leave_spinning = 1;
 	btrfs_set_trans_block_group(trans, inode);
 
 	key.objectid = inode->i_ino;
@@ -167,9 +168,9 @@ static noinline int insert_inline_extent(struct btrfs_trans_handle *trans,
 			cur_size = min_t(unsigned long, compressed_size,
 				       PAGE_CACHE_SIZE);
 
-			kaddr = kmap(cpage);
+			kaddr = kmap_atomic(cpage, KM_USER0);
 			write_extent_buffer(leaf, kaddr, ptr, cur_size);
-			kunmap(cpage);
+			kunmap_atomic(kaddr, KM_USER0);
 
 			i++;
 			ptr += cur_size;
@@ -1452,6 +1453,7 @@ static int insert_reserved_file_extent(struct btrfs_trans_handle *trans,
 	path = btrfs_alloc_path();
 	BUG_ON(!path);
 
+	path->leave_spinning = 1;
 	ret = btrfs_drop_extents(trans, root, inode, file_pos,
 				 file_pos + num_bytes, file_pos, &hint);
 	BUG_ON(ret);
@@ -1474,6 +1476,10 @@ static int insert_reserved_file_extent(struct btrfs_trans_handle *trans,
 	btrfs_set_file_extent_compression(leaf, fi, compression);
 	btrfs_set_file_extent_encryption(leaf, fi, encryption);
 	btrfs_set_file_extent_other_encoding(leaf, fi, other_encoding);
+
+	btrfs_unlock_up_safe(path, 1);
+	btrfs_set_lock_blocking(leaf);
+
 	btrfs_mark_buffer_dirty(leaf);
 
 	inode_add_bytes(inode, num_bytes);
@@ -1486,8 +1492,8 @@ static int insert_reserved_file_extent(struct btrfs_trans_handle *trans,
 					  root->root_key.objectid,
 					  trans->transid, inode->i_ino, &ins);
 	BUG_ON(ret);
-
 	btrfs_free_path(path);
+
 	return 0;
 }
 
@@ -2118,6 +2124,7 @@ noinline int btrfs_update_inode(struct btrfs_trans_handle *trans,
 
 	path = btrfs_alloc_path();
 	BUG_ON(!path);
+	path->leave_spinning = 1;
 	ret = btrfs_lookup_inode(trans, root, path,
 				 &BTRFS_I(inode)->location, 1);
 	if (ret) {
@@ -2164,6 +2171,7 @@ int btrfs_unlink_inode(struct btrfs_trans_handle *trans,
 		goto err;
 	}
 
+	path->leave_spinning = 1;
 	di = btrfs_lookup_dir_item(trans, root, path, dir->i_ino,
 				    name, name_len, -1);
 	if (IS_ERR(di)) {
@@ -2515,6 +2523,7 @@ noinline int btrfs_truncate_inode_items(struct btrfs_trans_handle *trans,
 	key.type = (u8)-1;
 
 search_again:
+	path->leave_spinning = 1;
 	ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
 	if (ret < 0)
 		goto error;
@@ -2661,6 +2670,7 @@ delete:
 			break;
 		}
 		if (found_extent) {
+			btrfs_set_path_blocking(path);
 			ret = btrfs_free_extent(trans, root, extent_start,
 						extent_num_bytes,
 						leaf->start, root_owner,
@@ -3466,6 +3476,7 @@ static struct inode *btrfs_new_inode(struct btrfs_trans_handle *trans,
 	sizes[0] = sizeof(struct btrfs_inode_item);
 	sizes[1] = name_len + sizeof(*ref);
 
+	path->leave_spinning = 1;
 	ret = btrfs_insert_empty_items(trans, root, path, key, sizes, 2);
 	if (ret != 0)
 		goto fail;